J.R. Smith spoke in a whisper, but his words were loud in their significance, biting criticism of his Knicks teammates in their no-show of a home opener. He basically said his team quit, without using the word.

“When we stopped competing at the end of the third, fourth quarter, we could all tell,” Smith said after the Bulls embarrassed the Knicks at the Garden, 104-80. “They felt as though they smelled blood in the water. We just couldn’t do anything about it.

“We put our heads down and tucked our tails, and we can’t do that at home.”

The Knicks were competitive early, trailed by 10 points at halftime, but were run out of the building after intermission, trailing by as many as 35 in the fourth quarter, boos filling the arena.

Smith said it’s time for the Knicks to stop over-thinking the triangle offense’s complexities and just play. He wasn’t suggesting veering away from the offense — Smith said he is all in, willing to sacrifice his offense for defense — but the enigmatic shooting guard also said he believes the Knicks were too mechanical against the Bulls.

“I don’t think we can be just thinking, thinking, thinking,” said Smith, who was held to six points on 2-of-8 shooting in 22 minutes. “Right now it’s time to react. If somebody just kicks down your mom’s door and takes what they want, I think you have to react, you can’t sit there thinking what should I do next.

By the time it’s over, everything’s going to happen.”

He challenged his teammates to show up with the intensity and passion Thursday night in Cleveland that was lacking Wednesday. They will need to be far better against LeBron James, Kevin Love and Kyrie Irving at Quicken Loans Arena, which will be an atmosphere like very few regular-season games, as King James makes his long-awaited return after four years in Miami.

“This is something I’ve never seen before,” Smith said. “It’s almost like the Super Bowl for them. The first game of the year, so many acts and what not to start the season off, comedians coming. I don’t know what to expect, honestly.

“I don’t think we should watch the news, because it’s gonna be everywhere. It’s just a matter of staying focused and being locked in. Of course you want to be a part of history and stuff like that, but we want to be on the good side, the team that came out and beat those guys. We shouldn’t get caught up in the hoopla. Just go out and play.”